1. Field of the Invention
The present invention relates to a system for monitoring and treating at least one physiological condition of a patient. More particularly, the present invention relates to a system and method for providing a balanced, regulated treatment of the physiological condition based on monitoring and controlling one or more predetermined physiological parameters.
2. Discussion of Related Art
Healthcare professionals in intensive care facilities are often faced with treating patients for one type of physiological condition while monitoring at least one of a host of physiological parameters. It is often necessary to deliver various medications to patients in order to control these physiological parameters. Monitoring and controlling multiple physiological parameters for a plurality of patients requires a great deal of time and resources from healthcare professionals. With ever increasing shortages in healthcare staff, workloads have been shown to be directly proportional to an increase in the occurrence of errors in medication delivery. Errors in medication delivery occur more frequently than commonly known and many of the errors are life threatening. In addition, these errors often go undiscovered and/or unreported.
There are several physiological conditions that are monitored in an intensive care setting, namely hypoglycemia, blood clotting, and the overall physiological stability of the patient. Typically, however, healthcare providers will measure only one physiological parameter, such as glucose level, prothrombin time, blood flow, hemoglobin level, heart rate, blood pressure, arterial oxygen concentration and other cardiac output, to treat the specific physiological condition under examination. Based on this measurement or a series of these measurements, the provider delivers medication to the patient in order to stabilize the physiological parameter and thus treat the physiological condition.
The control of glucose levels in seriously ill patients has proven to be a significant problem. Hyperglycemia is a frequent consequence of severe illness, occurring in both diabetic and non-diabetic patients, due to altered metabolic and hormonal systems, impaired gastrointestinal motility, altered cardiac function, increased catecholamine production, altered hepatic gluconeogenesis, relative insulin resistance and increased corticosteroid levels. Symptoms associated with elevated levels of blood glucose include dehydration, weakness, greater risk of poor healing and infection, frequent urination, and thirst. Infusion of insulin has proven an effective method for treating hyperglycemia. However, insulin infusion without proper glucose level monitoring can lead to problems with hypoglycemia.
Hypoglycemia in both diabetic and non-diabetic patients is one physiological condition that is monitored in an intensive care and/or other acute medical setting. Hypoglycemia is a common problem with severely ill patients and is defined as the fall of blood and tissue glucose levels to below 72 mg/dl. Symptoms associated with decreased levels of blood and tissue glucose levels are weakness, sweating, loss of concentration, shakiness, nervousness, change in vision and if untreated, loss of consciousness, possible seizures and neurological sequelae such as paralysis and death. Treatment in the case of both hyperglycemia and hypoglycemia involves monitoring and controlling the patient's glucose level.
Medical studies have established a direct correlation between morbidity and mortality in intensive care patients and the degree of glucose control. The use of intravenous insulin has vastly increased the efficacy of glucose control and has proven to be superior to conventional insulin treatment in reducing morbidity and mortality among patients in intensive care.
Data provided in medical studies indicates that hypoglycemia occurs in 3.8%-4% of all patients when glucose is measured every 2 hours. In other words, the average patient has a hypoglycemic episode every 2 to 4 days. The mean time that patients spent in the intensive care unit in these studies was between 2.5 and 10 days. Thus, theoretically, the average patient would have at least 1 and possibly up to 5 episodes of hypoglycemia during their intensive care unit stay. To reduce the risk of hypoglycemia, the burden is on nurses to monitor patient glucose levels every 1 to 1.5 hours. In addition, nurses must implement increasingly complex procedures to monitor and control patients' glucose levels. This level of attention by healthcare professionals is not practical for busy hospital intensive care units. Furthermore, as a result of increases in medical malpractice claims, stricter control regimens have been imposed on hospital staffs. These control regimens are often complex and increase the already heavy burden on health care professionals.
Systems and methods for monitoring and controlling glucose levels in intensive care units are known. One such system requires manual adjustment of the intravenous insulin using a single normogram or algorithmic sequence, where various adjustments are manually made over time. This system involves periodic measurements (typically hourly) of the patient's blood glucose level taken by nursing staff. The nursing staff must then obtain orders from a doctor to adjust the amount of insulin being delivered to the patient in an effort to maintain the patient's blood glucose level within a desired range. This method is time consuming, costly and prone to error.
Also known are systems and methods for monitoring and controlling blood glucose levels with an algorithm having a modifier to adjust the patient's insulin rate based on the level of the immediately preceding glucose measurement. If the glucose level declines too quickly, a negative modifier slows the intravenous insulin delivery rate. Alternatively, if the glucose level increases too quickly, the negative modifier increases the intravenous insulin delivery rate. This system is complex to run because multiple glucose level measurements are necessary to determine the rate of the intravenous insulin delivery. Thus, healthcare professionals spend additional time and resources on using this type of system.
Further, neither of the aforementioned systems includes a counterbalancing glucose infusion algorithm. The use of intravenously delivered insulin alone is unbalanced in that no counteracting glucose solution is activated when measurements indicate that glucose is declining. In systems currently available, a patient on intravenous insulin is given a bolus, or a concentrated infusion of glucose to counteract hypoglycemia, only after his or her glucose level reaches a particular level. While the insulin rate may be reduced or stopped altogether at low glucose levels, the effects of insulin at the tissue level persist and hypoglycemia may nevertheless develop. Moreover, insulin infusion rates cover a wide distribution of glucose readings. For example, minimum rates of 0.5-1.0 units of insulin per hour may start at glucose levels from about 80 to about 120 mg/dl, while maximum rates of insulin delivery may start at glucose levels as low as about 10 units per hour to those which have no apparent upper endpoint. Because of these variables, it is difficult for healthcare professionals to determine the precise time to provide counterbalancing glucose infusions. Accordingly, there exists a need for a computerized monitoring and control system that assists healthcare professionals in monitoring hypoglycemia by measuring glucose levels, projecting future values and setting the infusion rate of glucose and insulin based on these values.
It would also be useful to monitor and control blood clotting in seriously ill patients. Blood clots (fibrin clots) result from coagulation of the blood. A blood clot that forms in a vessel or within the heart and remains there is called a thrombus. A thrombus that travels from the vessel or heart chamber where it formed to another location in the body is called an embolus, and the disorder, an embolism. For example, an embolus that occurs in the lungs is called a pulmonary embolism. Thrombi and emboli can firmly attach to a blood vessel and partially or completely block the flow of blood in that vessel. This blockage deprives the tissues in that location of normal blood flow and oxygen. Thus, it is important to monitor and control blood clotting in seriously ill patients to reduce the risk of stroke and other life threatening complications.
However, monitoring and controlling blood clotting is inherently complicated. Patients who receive excessive amounts of an anticoagulant can suffer from unusually heavy bleeding episodes. This can be particularly dangerous for intensive care patients who have sustained surgical wounds, the elderly who are especially sensitive to anticoagulants, heart patients, and children. Thus, healthcare professionals typically monitor patients for signs of excessive bleeding in order to provide the correct doses of either a coagulant or an anticoagulant. Presently available methods include observation and manual delivery of these medications. Accordingly, there also exists a need for a computerized monitoring and control system that assists healthcare professionals in monitoring blood coagulation by direct or indirect measurement of coagulation status, including intrinsic or extrinsic clotting factors, projecting future values and setting the infusion rate of a blood coagulant and anticoagulant based on these values.
As yet another example, health care professionals also monitor the overall physiological stability of intensive care unit patients by monitoring physiological parameters such as blood flow, heart rate, blood pressure, hemoglobin levels, cardiac output, arterial oxygen concentration and other factors. All of these physiological parameters are affected by vasodilators and vasoconstrictors.
Electron beam CT scanners for tracking blood flow by acquiring images of pulmonary anatomy and function are known. By using an appropriate blood flow model, regional parenchymal time-intensity curves, sampled from dynamic CT scans of a bolus contrast injection, can be used to calculate regional blood flow, regional air, blood and tissue percentages, in addition to regional contrast mean transit times and arrival times. Computerized systems are used to convert data taken from the scans into blood flow calculations, color coded images, and the like.
Thermographic cameras are also known and are used to record infrared radiation, or heat, rather than visible light. In this manner, a thermographic camera identifies differences in blood flow because warmer areas record greater blood flows. Ultrasound monitoring, also known, measures the speed with which blood flows through blood vessels. This method can detect blood vessel constriction as well as blood flow abnormalities.
While all of these systems are useful to monitor patient blood flow, they do not provide a means for controlling the blood flow of a patient nor do they provide an effective, easy way of combining data related to other parameters such as blood pressure, heart rate, hemoglobin level, arterial oxygen concentration and cardiac output to monitor overall patient stability.
Vasodilation is one parameter used to gauge overall physiological stability of a patient. It is well known that nitric oxide is a naturally occurring vasodilator present in the vascular endothelium of body tissue. Synthesis of nitric oxide is modulated by shear stress in the vessel walls. This helps match vessel caliber to blood flow. At a cellular level it works by converting guanylyl cyclase to cyclic glycomacropeptide (GMP) which in turn relaxes vascular smooth muscle. The use of inhaled nitric oxide is widely known as a means to reduce pulmonary vascular resistance and improve the ventilation/perfusion relationship in patients with acute hypoxic respiratory failure, acute lung injury or right ventricular overload.
One technique that is used to boost nitric oxide production in severely ill patients on ventilators involves manually adding a continuous stream of nitrogen/nitric oxide mixture into an inspiratory limb of a ventilator, usually as close to the ventilator as possible to give time for the nitric oxide to mix before it reaches the patient. A monitor that analyzes nitric oxide and nitrogen dioxide is placed at the distal end of the inspiratory limb. The flow of nitrogen/nitric oxide is controlled by a needle valve and rotameter and manually adjusted to give the required inspired concentration.
Another technique commonly used to boost nitric oxide production involves administering L-arginine to ICU patients. One such technique includes ingestion of orally administered L-arginine. Administration of enteral L-arginine is limited in that noticeable increases of nitric oxide production in patients generally occur 2 to 4 hours after ingesting the L-arginine. Another technique involves parenteral administration of L-arginine, including intravenous injections. Other techniques for boosting nitric oxide levels in patients include pulsatile or continuous infusion of insulin or phosphodiesterase.
Vasoconstriction is another parameter used to gauge the overall physiological stability of a patient. Vasoconstriction is achieved via intravenously administered medications, such as endothelin, endothelin like compounds, sympathomimetics and vasopressin like compounds. The use of such pulmonary vasoconstrictors increases the efficacy of nitric oxide and can be instrumental in providing a required balance between vasoconstriction and vasodilatation for physiologically stabilizing a patient. However, heightened levels of vasoconstrictors, particularly endothelin, can lead to pulmonary artery hypertension and heart failure.
Because both of the foregoing techniques involve the manual introduction of medication into patients, they are inherently prone to error. Accordingly, there exists a need for computerized monitoring and control system that assists healthcare professionals in monitoring blood flow by measuring and controlling vasodilatation and vasoconstriction, projecting future vales of these parameters and setting the infusion rate of medications to treat these parameters.
Based on the foregoing examples and in light of increasing shortages in intensive care personnel, there exists an acute need for a balanced physiological monitoring and control system that uses an intelligent control device and a multi-channel delivery manifold for controlled delivery of a plurality of medications that impact a monitored physiological parameter in order to stabilize and balance a physiological condition in a patient.